Carrier based formulation of microbial cells has long been established for applications in various fields like agriculture (Meyer, 2003; Trivedi and Anita Pandey, 2008; Trivedi et al., 2005), pharmaceutical (Tanaka et al 1993, Frokjaer and Hovgaard, 2000) and industrial (Tanaka et al., 1993) sectors. The aim of formulating viable cells to facilitate the delivery and handling processes and to ensure that adequate cell viability is sustained to increase the efficacy of the cells (Filho et al., 2001). Importance of native strains and ecological specificity while selecting the microbial inoculates for a specific environment is also realized (Pandey et al., 1998). For bioremediation purposes, formulated microbial cells are often applied using wet (liquid) formulations i.e by spraying inoculums suspensions on targeted sites, or using dry (solid) formulations where granules or dust are sprayed instead (Brar et al., 2006). The selection on the type of formulation developed and used is dependent on the nature of the active cells and factors related to the site of application such as application to aquatic or terrestrial landscapes, temperature, etc (Tu and Randall, 2005; Sabaratnam and Traquair, 2001). Most often, dry formulations are generally preferred over wet formulations because they provide extended shelf life and are easier to store and transport. In agriculture, various carriers have been used for the protection of bioinoculants such as alginate beads, charcoal, sand, sawdust and sugarcane bagasse, etc (Arora et al., 2008). Biodegradation of petrol by bacterial formulated with bentonite-based formulations has been reported by Ting et al, 2010. Plastic materials are widely used in industry, agriculture and day-to-day life. Because of their high durability, they accumulate in the environment at the rate of 25 million tons per year(Orhan and Buyukgungor, 2000). Thermoplastics are inert materials whose backbones consist of only long carbon chains. Their high hydrophobic level and high molecular weight characteristic structure makes them non-biodegradable. However, some microorganisms have been reported to utilize polyolefins with low molecular weight (Yamada-Onodera et al., 2001). The resistance of polyethylene to biodegradation stems for its high molecular weight, three-dimensional structure, and hydrophobic nature (Hadad et al, 2005) and lack of functional groups recognizable by existing microbial enzyme systems (Chiellini et al, 2003). Major strategies to facilitate PE disintegration and subsequent biodegradation, were focused on the direct incorporation of carbonyl groups within the backbone or on their in-situ generation by pre-oxidant additives like polyunsaturated compounds, transition metal ions and dithiocarbamates. These functional groups act as initiators of thermal and photo-oxidation of the hydrocarbon polymer chains (Chiellini et al, 2003), thereby increasing the surface hydrophilicity and facilitating biodegradation by micro-organisms. EI-Shafei et. al (1998) investigated the ability of fungi and Streptomyces strains to attack degradable polyethylene bags containing 6% starch. Gilan et al., 2004 isolated a stain of Rhodococus ruber that could colonize & degrade PE. Fungal attachment has been reported on the surface of the LDPE pieces buried in soil mixed with sewage for 10 months, indicating possible utilization of plastic as a source of nutrient (Shah et al., 2008). The isolated fungal stains were identified as Furasium sp., Aspergillus terreus and Penicillum sp, respectively. In another study, two marine microorganisms viz. Bacillus sphericus and Bacilius cereus have also been recently reported for degradation of LDPE and HDPE (Sudhakar et al., 2008). Further a consortium of Bacilius cereus, Bacilus pumilus species and Anthrobacter sp was reported to degrade both LDPE as well as HDPE to an extent of nearly 22% within a period of two weeks (Satlewai et al., 2008). Similarly, a consortium of four different bacteria genara, Viz. Bacterium Te68R, Bacillus cereus, Proteobacterium Sp. and Anthrobacter luteolus has been reported to degrade non-poronized and poronized forms of LDPE (Soni et. al., 2009).
With a view of developing microbial inoculants for LDPE biodegradation, the described bacterial strains were isolated and have been reported earlier (Satlewel et al, 2008; Soni et al, 2008; Negi et al, 2009; Kapri et al, 2010 Sah et al, 2010; Kapri et al 2010) by our group.